In the wake of the massive Capital One data breach incited by a misconfigured web app firewall, we are throwing in a .NET open source library vulnerability that demonstrates the pervasiveness of privilege escalation attacks across web apps for good measure.

CVE-2019-1010199

Vulnerability Score: Medium — 6.1 (CVSS v3.0)

Platform: .NET 

Component: ServiceStack 

Affected versions: 4.5.14

It is a perilous time for ServiceStack users, a widely-used .NET based library.
The problem lies with the ServiceStack ecosystem, where a JavaScript-based Cross-Site Scripting (XSS) vulnerability could allow attackers to inject client-side code or scripts into web browsers viewed by other users. This means that said script is activated when it is read by an unsuspecting user’s web browser or web application. The web page or application then acts as an attack vector that delivers the malicious script to the user’s browser.

A web page or application is made vulnerable to XSS if it executes unsanitized user input for web servers to generate output – this user input must then be parsed by the victim’s browser to potentially compromise the system. We will note that though XSS attacks are possible across many languages (e.g. VBScript, ActiveX, Flash, CSS), they are, however, most common in JavaScript (as with this vulnerability) as this language is most commonly used as a client-side scripting language to support a bulk of web browsing experiences. 

In the context of this vulnerability within ServiceStack Framework 4.5.14, the flawed component is the query code used to execute the GET request. And with the web browser’s lack of server-side validation serving as the attack vector, this means that browser encoding is bypassed which could then compromise unsuspecting users’ browsers upon opening a crafted URL. The resulting impact is that a potentially malicious JavaScript code (aka unsanitized user input) would be reflected in the server response during execution for web browser output generation.

Such cross-site scripting vulnerabilities are often used by attackers for privilege escalation issues, especially to bypass access controls when two web pages are of the same origin (i.e. two URLs sharing the same protocol, port (if specified), and host).

This unauthorised access could then lead to security breaches such as data theft and password dumping. It is thus imperative that affected frameworks immediately download the patched version in 5.2 or later to avoid sensitive data violations.

With JavaScript being a key programming language that supports web development, it is imperative that we keep our guard up against unwanted intrusions to ensure seamless and secure provision of web services. We certainly hope this detailed analysis of this .NET vulnerability has galvanized you into taking active measures to avoid systemic data breaches. Until next time!

Sign up here to download the Meterian client today. You’ll get an instant analysis of your first project for free.  See the risks immediately and know which components to remove or upgrade to secure your app.